Stefan N. Oline is a Neuroscience Ph.D. Candidate in the Integrative Biology program

Stefan came to Lehigh after earning a Bachelor of Science in Psychology at the University of Delaware. While there, Stefan worked as an undergraduate researcher, investigating platforms to interface electrical devices with peripheral nerves. This exposure to the boundary between mind and environment fuelled an interest in sensory processing. Specifically, he was interested in how external stimuli are represented and interpreted by the brain. In the summer of 2009, Stefan entered Lehigh’s doctoral program, and joined the auditory neuroscience lab of Dr. Michael Burger to investigate these questions.

The Burger lab studies how neurons function in the hearing circuit. In addition to its clinical relevance, auditory circuitry is a powerful system for studying sensory processing because the signal (sound) is well defined, with distinct physical properties. More specifically, the Burger lab is interested in how computation in auditory circuitry imparts on listeners the ability to localize sounds in a three-dimensional environment. For instance, in order to locate a sound source on the horizontal plane, the brain compares the arrival time of sound between the two ears. Neurons in auditory circuitry have special adaptations that allow them perform this task with microsecond precision. Stefan’s work, within this broader framework, focuses on how neurons that receive auditory nerve input are able to selectively filter out noise, while allowing auditory signals to pass to higher brain centers.

Sound localization requires that timing information be maintained in the first few synapses of the brain. In the ear, sound information is acquired differentially along the cochlea. High frequency sounds are represented near the eardrum, while low frequency sounds are represented near the apex (see figure). This is complicated by a vast range of audible frequencies, which spans more than three orders of magnitude. Neurons that process information on low frequency sounds (red) must therefore use different computational strategies than those processing higher frequencies (blue). Additionally, physiological constraints such as maximum neuron firing rate, number of synaptic input fibers, and neurotransmitter availability limit the range within which neurons may faithfully represent a sound. Nevertheless, the remarkably complex task of sound localization is achieved by insects, birds, reptiles, and mammals, each with different strategies.

Stefan’s dissertation work has focused on synaptic auditory nerve inputs to cochlear nucleus neurons. His recent publication investigated short-term synaptic plasticity of auditory nerve synapses, or how the strength of an auditory nerve synapse onto a cochlear nucleus neuron changes in response to recent activity. He showed that synaptic plasticity of these synapses is distributed along the frequency axis. Surprisingly, auditory nerve synapses to high frequency neurons are much more robust than their low frequency counterparts. He then demonstrated that this distribution in synaptic plasticity is primarily due to a lack of neurotransmitter availability at low frequency inputs. Currently, he is investigating the subsequent effects of this differential plasticity on postsynaptic signal processing. Understanding the range of computational strategies used in this elegant circuit may allow for a more comprehensive and fundamental understanding of synaptic processing for all neurons that receive a more complex complement of inputs.

Aside from his dissertation work, Stefan served for two years as President of the Biology Organization of Graduate Students. Outside of the office, he participates in public outreach programs, such as Science Night at his niece’s elementary school, and as a STEM career panelist at a local high school where his fiancée, Amanda, teaches English and Journalism. He also enjoys observational astronomy, and coaches the department’s softball team, The Biohazards.

Stefan’s most recent work was recently published in The Journal of Neuroscience.